1. Field of the Invention
Embodiments of the invention generally relate to flow measurement apparatus and methods.
2. Description of the Related Art
In the petroleum industry, as in many other industries, ability to monitor flow of fluids in process pipes offers considerable value. Some approaches to determining flow rate of a fluid utilize a meter, referred to as a Sonar flowmeter, to detect and analyze pressure variations traveling with the fluid. However, these pressure variations due to sensitivity of the meter and signal-to-noise ratio limitations may not be detectable under some operating conditions.
For example, dynamic pressures of the flow not being above a certain minimum threshold can limit ability to detect the pressure variations. Since the dynamic pressure is based on velocity of the flow and density of the fluid, the meter may not enable measuring flow rates as slow as desired, especially for gas-rich fluids that have relatively lower densities. Further, changes in flow regimes such as occur through a nozzle can cause reductions of turbulence within the flow as the flow accelerates through the nozzle and tends to laminarize. Due to turbulence being what provides the pressure variations detected by the meter, structures that change the flow regime and may be beneficial or necessary for other reasons can adversely impact ability to detect the pressure variations, which may already be weak depending on the dynamic pressure of the flow. Redeveloping of a turbulent boundary layer occurs away from the structure that changed the flow regime. However, location of the meter where turbulent structures redevelop increases a length requirement for the meter, thereby necessitating greater installation space that may not be available in some situations, such as on offshore rigs. This excess length also adds to weight making transport more difficult and causes the meter to be more expensive and time consuming to manufacture.
Therefore, there exists a need for improved apparatus and methods for sensing flow velocity of a fluid based on detecting pressure variations traveling with the fluid.